1. Field of the Invention
The present invention relates to manually actuated, hydraulically operated tools of the type having working elements such as jaws or cutters which close over a workpiece. More particularly, the invention relates to a hand tool having a hydraulic circuit contained entirely within a housing containing two pistons. One piston converts manual input force to fluid pressure. The other piston converts fluid pressure to output force for imposing on the work. The tool enables three speeds of closure of jaw or corresponding tool movement at one input speed.
The field of endeavor most likely to benefit from this invention is the construction industry in that the device is specifically intended for use in creating effective hand tools which are often used in the building trades. However, the general fields of mechanical assembly and automotive repair could also benefit from the apparatus herein disclosed. For example, any process requiring crimping, bending, punching, cutting, pressing, etc. could significantly benefit from the performance characteristics of the instant hydraulic tool.
It can be appreciated that the potential field of use for this invention are myriad and the particular preferred embodiment described herein is in no way meant to limit the use of the invention to the particular field chosen for exposition of the details of the invention.
2. Description of Related Art
Gripping, clamping, pressing, and punching tools frequently employ hydraulic circuits for actuating solid moving parts of the tool. Hydraulics are quite practical to magnify manual force which can be applied to a work piece. Magnification of force is readily accomplished by varying respective areas of driving and driven components, such as a pump plunger and a driven piston, subjected to fluid pressure. Overpressure relief valves and manual release valves are also easily incorporated into hydraulic circuitry. However, the incorporation of such valving features has previously added considerable expense and complexity to the mechanism. This expense has been a major reason that small hydraulic hand tools have not achieved widespread success in the marketplace.
Thus, there is a need to provide hydraulic tool of reduced complexity and thus of reduced cost.
Furthermore, when a conventional manual hydraulic tool, such as an automotive jack, is designed to develop great force it requires a large input stroke (or many smaller such strokes) to generate a small output motion. This is tedious and wasted motion during the period when a magnified output force is not needed. For example, when a tool has not yet engaged its work, it is wasteful to have to provide very long (or very many) input strokes to move the tool a very small distance toward its eventual working position. Most prior art hydraulic hand tools are designed to provide only one mode of operation, that being intended for applying great force after the point of contact with the work piece. When initially positioning the tool to the work, pumping a small volume of fluid per stroke so as to develop high pressure for operating the tool is pointless when no significant output resistance is encountered.
Thus, there is a further need to provide not only a tool which could rapidly advance the driven piston to a working piston with minimal mechanical input, but also which hydraulically magnifies the mechanical input to impart very high output forces once the work is engaged.